1. Field of the Invention
This invention relates to air-powered tools, and more particularly to a hand-held turbine-driven orbital sander employing a minimum of housing parts to form a nozzle, turbine air chambers, and a valve chamber. The housing also provides an attenuation system which simultaneously reduces turbine air inlet noise and turbine vane noise.
2. Description of the Prior Art
Air-driven abrading devices have generally required the use of several housing components and their attendant extra hardware thereby increasing their relative size and costs of manufacture. U.S. Pat. No. 3,722,147 discloses a turbine powered abrading device for walls and floors. A dome-shaped housing encloses a turbine which draws air in an axial flow upwardly from the worksurface. There is no "nozzle" per se, and any "on-off" controller must be located in the conduit member and away from the unit. Also, its housing does not provide turbine vane or air inlet noise attenuation, nor does it permit hand-held operation.
Other air-powered devices suffer similar disadvantages. U.S. Pat. No. 2,904,817 shows a turbine-powdered rug brush in which a valve plate must be secured in one of several positions by an external control knob. Although the rug brush is enclosed by two housing members, it contains no structural members to withstand vertical pressure such as is generated in a hand-held sanding tool, nor do its housing members provide a turbine noise attenuation system.
U.S. Pat. No. 3,262,199 shows a turbine-powered hair clipper. The nozzle includes a single curved air passage designed to direct air tangentially into the turbine, but it does not interrupt the line of sight from the nozzle entrance to the turbine. Also several housing components are required to enclose the turbine, cutting mechanism, and nozzle. Two housing members must first be removed from a mounting base before an operator can access the screws, as for cleaning the turbine chamber. Furthermore, the housing does not define a valve chamber.
Patents describing vacuum cleaners which generate air flow, but which are not themselves air-driven include the following: U.S. Pat. No. 3,246,359, which teaches an electric motor-driven vacuum cleaner in which an air inlet is integral with one housing member, but which lacks a valve chamber; U.S. Pat. No. 2,342,905, which shows the use of a plurality of perforations in a muffler, but also indicates that the perforations must be used in conjunction with sound-deadening material such as felt; and U.S. Pat. No. 2,340,437, which teaches the use of a resonant chamber and communicating slots in a vacuum cleaner muffler. However this muffler must match the volume of the resonant chamber to an entire range of frequencies, there being no single dominant wavelength. Also neither of the last two mentioned patents teach the use of a resonant chamber in combination with means for attenuating air inlet noise, nor do they show the use of a nozzle to form a noise attenuation system.